Hot cathode device



May 19, 1931.

F. S. MCCULLOUGH HOT CATHODE DEVICE Filed vJan.' 5 1926 xNvENj-aR Patented May 19, 1931 UNITED STATES PATENT FFICE HOT CATHODE DEVICE Application led January 5, 1926.

ment associated therewith in such manner as to deliver heat thereto.

In certain types of hot cathode devices it has heretofore been proposed to form thecathode in the form of a shell and to have a heating wire within the shell. This heating wire has either been supported within the shell by a suitable supporting means, or has been embedded within a mass of porcelain or other heat resist-ant material, the shell forming the cathode being fitted about this mass of porcelain.

The present invention relates particularly to an improvement in such devices, and has for its object to provide a construction wherein one end of the heating element is con: nected directly to the cathode element to materially simplify the construction of the tube and to increase its eiiiciency. The present i11-V f the electrodes of a two electrode cathode device with the envelope thereof illustrated by a dotted outline.

In the drawing the dotted outline designates a suitably constructed envelope, preferably of glass, which is evacuated. Support-Y serial No. 79,352.

wire 8. The shell 5 is connected to and supported by a second lead-in wire 9 whose point of attachment to the cathode is preferably at the end opposite the point where the heater wire connects to the cathode, while a third lead-in wire 10 is attached to the plate 3.

In operation a source of alternating current may be connected across the lead-in wires 8 and 9. The current flowing through the heating wire 6 will serve to heat the shell 5 to a point where it will sustain electron emission to effect the operation of the tube.

The arrangement herein provided has several advantages. In the iirst place, there need be only three lead-in pins or connections at the base of the tube. By reason of the fact that one end of the heating wire is connected directly to the cathode instead of to another lead-in wire or post, as has heretofore been the practice, heat which would otherwise be conducted into the base is carried ldirectly to the cathode.

A further advantage of the construction resides in the fact that the tube can be assembled much more easily and rapidly by connecting the end of the heater wire directly to the cathode instead of to an external pin or post. It will be seen that the cathode is in series with the heater wire, preferably its entire length being in series, so that there is a current flow therealong during the operation of the tube.

I claim: Y p

An electron tube having a tubular cathode member, a heater wire having a loop inside the cathode member and extending longitudinally of said cathode tube, both ends of said wire being at the same end of the cathode, one end of said wire being connected to one end of the cathode, a heater current supply wire connected to the other end of the heater wire, and a second current supply wire connected to the cathode only at that end of the cathode opposite the end to which the heater wire is connected thereto.

In testimony whereof I have hereunto set my hand.

- FREDERICK s. MOCULLOUGH. 

